I also tried to get some power with Bosch 4s Only to kick 'em to the curb for OEM plugs...at over 10 clams each! I'm getting ready to dig deep for some Iridium plugs next, for HP, BUT YOU CAN BET those OEM plugs will be put away safely for a rainy day (at the price I payed). Toyota will tell you that the European plugs do not work well. Though I have not heard this about the splits, I would think similarly of them. I would only use platinum or iridium. I kept the bosch 4s for my 944. Cooky as it sounds nationally produced items are generally designed to work best with their own machines.